This invention relates to explosives and more particularly to polynitro organic explosives.
E. F. Witucki and M. B. Frankel, J. Chem. and Eng. Data, 24, 382 (1979), reported preparation of 2-fluoro-2,2-dinitroethyl pentafluorothioacetate from 2-fluoro-2,2-dinitroethanol and pentafluorothioacetyl chloride. The acethyl chloride was chosen as the --SF.sub.5 starting material because of its availability from SF.sub.5 Cl and ketene. E. F. Wituck and M. B. Frankel, Rockwell International UCRL report 13809 (1978), describe 2-fluoro-2,2-dinitroethyl pentafluorothioacetate as a dense, thermally stable, insensitive liquid.
We have recently prepared other polynitroaliphatic esters of pentafluorothioacetic acid using the Witucki et al., method and have found them to be liquids or very low melting solids. For instance:
______________________________________ Ester M.P. (.degree. C.) ______________________________________ 2,2-dinitropropyl pentafluorothioacetate 22 3-fluoro-3,3-dinitropropyl pentafluorothioacetate 28 3,3,3-trinitropropyl pentafluorothioacetate 32 ______________________________________
Thus, like the prior art 2-fluoro-2,2-dinitroethyl pentafluorothioacetate, these novel polynitroaliphatic esters of pentafluorothioacetic acid are limited to liquids or very low melting solids. This is a disadvantage because many applications require high melting solid explosives. Therefore, it would be desirable to have available higher melting pentafluorothio (SF.sub.5) explosives in order to provide a greater choice of physical properties for these types of compounds.
In U.S. Navy Case Ser. No. 71,604 entitled "Pentafluorothio Polynitroaliphatic Explosives," filed at the same time as this application by the same inventive entity (Michael E. Sitzmann and William H. Gilligan), compounds are disclosed and claimed which appreciably extend the range of physical properties available in SF.sub.3 explosives but they suffer a disadvantage in that they are synthesized from 2-pentafluorothioethanol. The disadvantage of using 2-pentafluorothioethanol is that it contains appreciable carbon and hydrogen in addition to the SF.sub.3 group. Thus, in order to attain maximum energy output, any polynitroaliphatic derivative of 2-pentafluorothioethanol must contain extra oxidant to totally combust this carbon and hydrogen to CO.sub.2, H.sub.2 O, and HF. Also this carbon and hydrogen will tend to dilute the effect of the SF.sub.5 group toward increasing the density of the polynitroaliphatic explosive. Therefore it would often be advantageous to employ an SF.sub.5 starting material that contains little, if any, carbon and hydrogen along with the SF.sub.5 group.